1. Field of the Invention
The present invention relates to a device which can be preferably used in an apparatus for preventing blurred images caused by unintentional movement of hands.
2. Related Background Art
The related background art will be described below.
Today, in a photographing camera, important operations for photographing such as determinations of exposure time, focusing, and so on are all automatically performed so that even a photographer who is not familiar with such operations seldom fails to take a good picture. However, failure caused by vibration of the camera body has been difficult to prevent.
Accordingly, a camera capable of preventing such failure caused by vibration of the camera body has been intensively studied. Among this kind of camera, a camera capable of the preventing failure caused by unintentional movement of hands of the photographer is eagerly being developed and studied.
The vibration of the hands at the time of taking a picture generally has a frequency in a range from 1 to 12 Hz. A fundamental method to obtain a good picture even if the camera body is vibrated by the hands at the time of releasing the shutter, is to detect such vibration of the camera body and drive a correcting lens according to the results of detection. Accordingly, in order to realize good photographing without a blurred image even if the camera body is vibrated, first, the vibration of the camera body has to be detected with precision, and secondarily, the deviation of the optical axis caused by the vibration has to be corrected.
Detection of the vibration (deviation) of the camera body can be carried out, principally by mounting, on the camera body, vibration sensors for detecting angular accerelation, angular velocity, angular displacement, and so on, as well as a deviation detection means for electrically or mechanically integrating the output of the vibration sensors to obtain the total angular deviation of the camera body. Further, a correction optical means is mounted on the camera body. This correction optical means is to be driven to shift the photographing optical axis according to the information from the deviation detection means. Thus, the blurred image can be reduced.
The outline of the blur suppression system using the angular deviation detection means will be described with reference to FIG. 28.
In FIG. 28, a reference numeral 43 designate a lens barrel. Angular deviation detection means (vibration detection means) 43p and 43y comprise angular velocity meters such as gyros, or the like, and integrators for integrating the angular velocities detected by the angular meters to obtain the angular deviation of the camera body. The angular velocity meter of the angular deviation detection means 43p detects vertical angular deviation, while that of the deviation detection means 43y detects horizontal angular deviation. Thus, the direction of the detection performed by the angular deviation detection means 43p is as indicated by an arrow 44p, while that of the means 43y by an arrow 44y. A correction optical means 45 has coils 46p and 46y for driving the optical means 45 and position detection elements 47p and 47y for detecting the position of the correction optical means 45. The correction optical means 45, which also has a position adjusting loop (described later), is driven corresponding to the target value outputted from the angular deviation detection means 43p and 43y in order to stabilize an image surface 48.
FIG. 29 is a perspective view showing an example of the construction of the correction optical means, wherein its constituents are disassembled.
A lens 71 is caulked in a support frame 72, in which a bearing 73y is tightly inserted. The bearing 73y supports a support shaft 74y so that the support shaft 74y can shift in its axial direction. The support shaft 74y has a small-diameter portion 74ya in order to engage with a hook 75a of a support arm 75. Also, a bearing 73p is tightly inserted in the support arm 75 in order to support a support shaft 74p so that the support shaft 74p can shift in its axial direction.
Note that, in FIG. 29, the back of the support arm 75 and a partial plan view thereof, which clearly shows the hook 75a, are also shown.
Light projector elements 76p and 76y are adhered into positioning holes 72pa and 72ya, respectively, of the support frame 72. The terminals of these light projector elements 76p and 76y are soldered with covers 77p and 77y, respectively, which are also adhered to the support frame 72 and serve as connection substrates. The support frame 72 has slits 72pb and 72yb, through which light beams emitted from the light projector elements 76p and 76y are incident on PSDs 78p and 78y (described later), respectively. Also coils 79p and 79y are adhered to the support frame, wherein the terminals of the coils 79p and 79y are soldered with the covers 77p and 77y, respectively.
Three support pins 711 having ball-shaped heads are inserted in their respective positioning holes of the lens barrel 710. The lens barrel 710 has a hook 710a for engaging with a small-diameter portion 74pa of a support shaft 74p.
Yokes 712p.sub.1, 712p.sub.2 and 712p.sub.3, and magnets 713p.sub.1 and 713p.sub.2 are adhered together so as to be alternately overlapped. Similarly yokes 712y.sub.1, 712y.sub.2 and 712y.sub.3, and magnets 713y.sub.1 and 713y.sub.2 are adhered alternately. Polarity of the magnets are indicated by arrows 713pa and 713ya.
The yokes 712p.sub.2 and 712y.sub.2 are fixed to recesses 712pb and 710yb, respectively, with screws.
Position detection elements 78p and 78y such as PSDs are adhered to senser bases 714p and 714y (of which 714y is not shown in FIG. 29), and covered with sensor marks 715p and 715y, respectively, wherein the terminals of these position detection elements 78p and 78y are soldered to a flexible substrate 716. Projections 714pa and 714ya (of which 714ya is not shown) of the sensor bases 714p and 714y are inserted into positioning holes 710pc and 710yc of the lens barrel 170, and then the flexible substrate 716 is fixed to the lens barrel 710 by means of a flexible substrate stay 717 and screws, lug portions 716pa and 716ya of the flexible substrate 716 are inserted through holes 710pd and 710yd, respectively, of the lens barrel 710, and fixed onto the yokes 712p.sub.1 and 712y.sub.1 with screws. The terminals of the coils and those of the light projector elements on the covers 77p and 77y are connected with land portion 716pb of the lug portion 716pa and land portion 716yb of the lug portion 716ya, respectively, of the flexible substrate 716, as well as, with polyurethane copper wires (three-wire strand).
A plunger 719 is fixed to a mechanical lock chassis 718, and set in a mechanical lock arm 721 provided with a spring 720, wherein the plunger 719 is rotatably fixed to the mechanical lock chassis 718 with a pivot 722.
The mechanical lock chassis 718 is fixed to the lens barrel 710 with screws, while the terminals of the plunger 719 are soldered with the land portion 716b of the flexible substrate 716.
Three adjusting screws 723 having spherical heads are thread fastened to and penetrated through the mechanical lock chassis 718 to hold, with the support pins 711, a slide surface 72c (indicated by slant lines) in between. The adjusting screws 723 are thread-fastened to the mechanical lock chassis 718 so as to be positioned to face to the slide surface with a small clearance.
A cover 724 is adhered to the lens barrel 710 to cover said correction optical means.
FIG. 30 shows a drive control system for the correction optical means shown in FIG. 29.
Outputs of the position detection elements 78p and 78y are amplified by amplifier 727p and 727y and applied to the coils 79p and 79y, respectively. As a result, the support frame 72 is driven and output of the position detection elements 78p and 78y varies. If driving direction (polarity) of each coil 79p/79y is set to coincide with the direction toward which output of the position detection element 78p/78y becomes smaller, (negative feedback), the coils 79p and 79y drive the support frame 72 to its stable position at which output of the position detection elements 78p and 78y becomes substantially zero. Note that adders 731p and 731y are circuits for adding output of the position detection elements 78p and 78y to commands 730p and 730y given from outside, that compensation circuits 728p and 728y further stabilize the control system, and that drive circuits 729p and 729y supply current to the coils 79p and 79y.
When commands 730p and 730y are given from outside to the system shown in FIG. 30B, through the adders 731p and 731y, the support frame 72 is driven exactly in correspondence to the commands 730p and 730y.
The technique employed in the control system shown in FIGS. 30A and 30B, in which the coils are controlled by negative feedback of the output of the position detection elements, is generally called "position control technique". In this case, when the movement of hands is given as the commands 730p and 730y, the support frame 72 is driven according to the movement of hands.
FIG. 31 is a circuit diagram for illustrating the details of the drive control system of the correction optical means shown in FIGS. 30A and 30B. Here, operations are described only with respect to the direction of the pitches (because operations in the direction of the yokes are the same).
Current/voltage conversion amplifiers 727a and 727b convert photo-current 727i.sub.1 and 727i.sub.2 generated in the position detection element 78p (comprising resistances R1 and R2) by the light projector 76p into voltages. Differential amplifier 727c calculates a difference between the output of the current/voltage conversion amplifiers 727a and 727b. The above current/voltage conversion amplifiers 727a and 727b, and the differential amplifier 727, and resistances R3 to R10 constitute an amplifier 727p shown in FIG. 30B.
A command amplifier 731a adds a command 730p applied from outside to a differential signal from the differential amplifier 727c. This command amplifier 731a and resistances R11 to R14 constitute an adder 731p shown in FIG. 30B.
Resistances 15 and 16, and a condenser C1, which serve as a well known phase advance circuit, constitute the compensation circuit 728p shown in FIG. 30B.
The output of the adder 731p is applied through the compensation circuit 728p to a drive circuit 729a, where a drive signal for the pitch coil 79p is generated. Thus the correction optical means is driven. The drive amplifier 729a, a resistance R17, and transistors TR1 and TR2 constitute the drive circuit 729p shown in FIG. 30B.
An adder amplifier 732a sums up the output of the current/voltage conversion amplifiers 727a and 727b (the total amount of light received by the position detection element 78p). The output of the adder amplifier 732a is applied to a drive amplifier 732, which drive the light projector element 76p according to the applied output. The adder amplifier 732a, the drive amplifier 732b, resistances R18 to R22, and a condenser C2 constitute the drive circuit for the light projector element 76 (not shown in FIGS. 30A and 30B).
The amount of light projected by the light projector element 76p is not stable and easily varies depending on temperature, for example. At the same time, the positional sensitivity of the differential amplifier 727c varies. However, by controlling the light projector element 76p by means of the above-mentioned drive circuit so as to obtain a constant total amount of received light, change in positional sensitivity can be reduced.
As described above, the correction optical means has the stable position at which the output of the position detection elements 78p and 78y becomes zero, and is driven toward the stable position according to the applied commands. Since the stable position is electrically adjusted at which the optical axis of the correcting lens 71 coincides with that of the photographing lens array in the lens barrel, the correction optical means is driven toward the optical axis of the photographing lens array.
The correction optical means is optically designed so that optical aberration of the whole photographing lenses may become as small as possible even when the correcting lens 71 is shifted in the direction vertical to the optical axis. When the amount of shift becomes great, optical aberration can not be negligible. The amount of aberration depends on focal length of the photographing lenses in various zoom modes and in focusing operation.
The relation between the amount of aberration and focal length will be described below with reference to FIGS. 32A and 32B.
In FIG. 32B, the correcting lens 71 in the photographing lens array 61 is driven as indicated by an arrow 62 for blur suppression, while the photographing lens array itself is moved along the direction Z of the optical axis according to chance of the focal length at zooming and focusing operation.
The amount of shift (distance from the zero position) of the correcting lens 71 driven in the direction shown by the arrow 62 varies according to the movement of hands, which varies, for example, as shown by a meandering curve 63 shown in FIG. 32A, as the time passes by. Suppose the release button of the camera is fully pushed (SW2 is ON) at a time 64. Then after a predetermined time lag 66, exposure is executed for a lapse 65. In FIG. 32A, during the lapse 65, the amount of shift (distance from the zero position) of the correcting lens becomes greater than an allowable driving range A and still within an allowable driving range A. The driving range B is the allowable aberration range at zoom-wide, while the driving range B is the allowable range at zoom-tele.
Therefore, when a picture is taken in the state as shown in FIG. 32A, no problem occurs at the time of zoom-tele mode (e.g. 300 mm), while aberration can not be negligible and deteriorates images at the time of zoom-wide mode (e.g. 75 mm).
Similar problems occur when the focal length is varied at focussing operation, wherein an object at the infinite-point causes no problem but an object close to the camera causes aberration.
FIGS. 33A and 33B are block diagrams schematically showing the construction of a camera employing the blur suppression system described above.
In FIGS. 33A and 33B, a vibration detection means 211 (designated by reference numerals 43p and 43y in FIG. 28) comprising deviation detection sensor such as an angular velocity detection means and a sensor output calculator for integrating output of the detection sensor to obtain deviation information, which is further amplified at a predetermined rate by the same calculator. A blur suppression change-over means 12 comprises a sample holder 212a and a differential circuit 212b. The sample holder (circuit) 212a is continuously executing sampling operations. Accordingly, the differential circuit 212b outputs a difference between the same values, that is, zero. A release means 217 is provided in the camera body. With half depression of the release button (when a switch SW1 is turned on), the release means 17 actuates an exposure preparatory means 242 for performing photometry and range measuring as well as for driving lenses to perform focusing. With full-depression of the release button (when a switch SW2 is turned on), the release means 217 actuates an exposure means 316 for lifting up and lowering a mirror as well as for opening and shutting the shutter.
When the release means 217 generates an ON-signal of switch SW1, the ON-signal is applied to the sample holder 212a of the blur suppression means 212 to bring the sample holder 212a into a holding mode, when the differential circuit 212b which adjusts the present value as time 0 starts continuous output of detected deviation (hereinafter referred to as the target value). The target value is applied through a blur suppression sensitivity altering means 246 (described later) to a buffer means 213 including a known filter circuit comprising of resistances and condensers, as well as to a buffer change-over means 214. The buffer change-over means 214 normally connects a switch terminal 214a with a terminal 14c. In other words, in the blur suppression mode, the buffer means 213 is disconnected with its terminal 214b separated from the switch terminal 214a.
A drive means 215 has the circuit construction shown in FIG. 30B, which receives the output of the position detection (output of the position detection elements 78p and 78y in FIG. 29) of the correction optical means 216 (designated by the reference numeral 71 in FIGS. 29 and 30A), and applies drive voltage to the coils 79p and 79y shown in FIG. 29. The target value is applied to the drive means 215 as a command, according to which the correction optical means 216 is exactly driven.
The blur suppression sensitivity altering means 246 performs amplification change (setting a first ratio) of the output of the buffer change-over means 214. The ratio of amplification is changed according to the output from a zoom information output means 311 and a focus information output means 310.
In order to execute sufficient blur suppression, the amount of shift (per unit time) of the correction optical means 216 is changed in correspondence with the change of the focal length of the lenses. In other words, the amount of correction of the correction optical means 216 against the amount of the movement of hands has to be changed according to the focal length. Such adjustment is necessary because the shift sensitivity (amount of correction carried out by the correction optical means 216 with respect to the image surface) of the correction optical means 216 varies according to the focal length. For example, suppose the shift (per unit time) of the correction optical means 216 required to sufficiently execute blur suppression against the movement of hand is equal to "1", then effective blur suppression has to be performed with 1/4 of the shift (per unit time) in the zoom-wide mode. Otherwise, the amount of correction for blur suppression becomes excessive in the zoom-wide mode and even increases the vibration of the camera body.
A ratio altering means 247 comprises an amplifier 247a (which sets a second ratio) for further changing the target value given from the blur suppression sensitivity change-over means 246 (wherein the amplifying rate is reduced to about 2/3), a differential circuit 247b for calculating the difference between the output of said amplifier 247a and the target value from the blur suppression sensitivity change over means 246, a sample holder 247c for holding the output of the differential circuit 247b at the time when the switch SW2 is turned on, a differential circuit 247d for calculating the difference between the output of the sample holder 247c and the target value from the blur suppression sensitivity altering means 246, and a change over means for connecting a terminal 247g with a switch terminal 247e only when the switch SW2 is turned on (which normally connects the switch terminal 247e with a terminal 247f, and with the terminal 247g during the output of a ratio change-over inhibiting means 314 is applied). The ratio altering means 247 applies the target value modified according to the first ratio until the switch SW2 is turned on and the target value modified according to the first ratio while the switch SW2 is turned on, to a drive means 215. The differential circuits 247b and 247d and the sample holder 247c hold the output of the sample holder 247c during the switch SW2 is turned on and memorize the difference between the output of the amplifier 247a and the target value (output of the blur suppression sensitivity altering means 246). The amplifier 247d further calculates the difference between thus obtained difference and the target value and sets it as a newly obtained target value. Thus, continuity at the time of turning on/off the switch SW2 operated by the switch terminal 247e is realized.
The amplifying ratio of the amplifier 247a is further varied according to the output of the zoom information output means 311 and the focus information output means 310. For example, the first ratio is set to be 2/3 in the zoom-tele mode, while the ratio is set to be 1/3 in the zoom-wide mode.
In other words, until the switch SW2 is turned on (before photographing operation), the original target value (obtained according to the first ratio) is reduced to 2/3. Thus, the amount of shift (per unit time) of the correction optical means 216 as well as power consumption can be reduced. At the same time, the blur suppression sensitivity is reduced to allow subtle framing (wherein subtle movement for framing is not canceled as vibration). And only at the time of exposure (when the switch SW2 is turned on), sufficient blur suppression is performed to prevent deterioration of the image caused by deviation of the image on the film surface.
When the first ratio is reduced to the 1/3, that is, to the second ratio in the zoom-tele mode until the switch SW2 is turned on, the photographer can not recognize the effect of blur suppression. In the zoom-wide mode, however, the photographer does not see the vibration of the image caused by slight movement of hands. Accordingly, while the photographer looks into the finder (after the switch SW1 is turned on until the switch SW2 is turned on), only large deviation has to be canceled, when the first ratio may be reduced to 1/3 (a predetermined second ratio).
With the above-mentioned construction, electric power can be saved.
The ratio altering inhibiting means 314 is actuated by operation of the photographer, and inhibits the first amplifying ratio of blur-suppression from being switched to the second amplifying ratio. That is, even when the switch SW1 is turned on, sufficient blur suppression is executed with the first ratio, which is useful when the photographer wants to look at the object carefully.
The output of the ratio altering inhibiting means 314 is applied to a switch means 247e of the ratio altering means 247. Then, the switch means 247e is kept in contact with the terminal 247g. The output of the ratio altering inhibiting means 314 is applied also to the ratio altering inhibition indicator means 312, which indicates that ratio altering is inhibited. A timer 2 (313) continuously output for a predetermined lapse from the time the switch SW2 of the release means 217 is turned on. At the time of trailing of the output of the timer 2, the ratio altering inhibiting means 314 is reset. As a result, ratio change-over inhibition is stopped at the end of every photographing operation. Needless to say, the photographer, if preferable, can stop ratio change-over inhibition.
Now, operation to stop blur suppression will be described.
In FIGS. 33A and 33B, when the switch SW1 of the release means 217 is turned off, the sample holder 212a resumes sampling, when the output of the amplifier 212b is zero and blur suppression is stopped.
If the buffer means 213, the buffer change-over means 214 and the timer 3 (317) shown in FIG. 33B are omitted, which is the construction shown in FIGS. 34A and 34B, the operation is carried out as follows.
With such construction, the output of the blur suppression change-over means 212 suddenly changes from the target value of deviation while the switch SW1 is on to zero. Accordingly, the correction optical means 216 is swiftly driven to the position satisfying zero target value.
In FIGS. 35A and 35B, at the time the switch SW1 is turned off, the correction optical means is swiftly driven from its present position. Such swift drive causes sudden change of framing, which disturbs the photographer. In order to present such disturbance, the buffer means 213 shown in FIG. 33B is employed.
In FIGS. 33A and 33B, when the switch SW1 is turned off, the output of the blur suppression means 212 becomes zero. This zero output is applied to the buffer means 213, whole output gradually becomes zero from the time the switch SW1 is turned on (because of the filter circuit of the buffer means 213). After the switch SW1 is turned off, for a predetermined time lag measured by the timer 3 (317), the switch terminal 214a of the buffer change-over means 214 is connected with the terminal 214b to set the output of the buffer means 213 as the target value of the shift of the correction optical means 216. In short, after the switch SW1 is turned off, the correction optical means 216 is slowly driven from the position at the time the switch SW1 is turned off to the position of zero target value, as shown by the solid line in FIG. 35B.
With the above-mentioned construction, unpleasant disturbance given to the photographer when the switch SW1 is turned off can be prevented. At the same time, power consumption can be reduced.
In the operation shown in FIG. 35B, however, the correction optical means 216 is slowly driven to its stable position after switch SW1 is turned off without performing blur suppression for the lapse 261. Such drive of the correction optical means 216 without blur suppression is waste of electric power, and drift of framing after blur suppression is not pleasant.